Cost control is critical to the management of enterprise. The costs analyze and problem solving of a medical unit can help a hospital to cost down and good for long term development. The purpose of this research is to analyze and solve the cost problem of a medical unit by using quality control circle activity. Six therapists in a rehabilitation center of a teaching hospital form a trace circle and try to improve the cost problem of the unit. We use professional evaluation to give proof for discussion and choose health insurance registration omission as our topic to handle. As health insurance registration and rehabilitation program were execute at the same time, so the omission of health insurance registration was a common problem of the medical unit. We used Quality Control story to take steps for problem solving, collected checklist recorded the registration omissions of the last three months and used 80/20 theory to choose the main factors to improve. We found that (1st item) patients' families did not understand the registration process (45%) and (2nd item) the therapists did not confirm the registration before therapies (35%) were the real reasons, and we planned the strategy to handle it. According to the record of registration omission checklists, the amount of registration omission was 20.3, after one month's strategy execution we calculated the improvement range. We found that after the improvement the amount of omission was 9, decreasing rate is 55.67%. The decreasing rates of registration omission caused by 1st and 2nd item were 60% and 63.99%. As the improvement is good, we compose it to a standard of process and keep executing it.